/* 下拉按钮样式 */
.dropbtn {
    background: url(../img/columns.gif) 	;
    color: black;   
    font-size: 16px;
    border: none;
    cursor: pointer;
	width:160px;
	height: 40px;
}

/* 下拉内容定位 */
.dropdown {
    position: relative;
    display: inline-block;
}

/* 下拉内容 (默认隐藏) */
.dropdown-content {
    display:none;
    position: relative;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
}

/* 下拉菜单的链接 */
.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
}

/* 鼠标悬浮状态 */
.dropdown-content a:hover {background-color: #1E90FF;}

/* 在鼠标移上去后显示下拉菜单 */
.dropdown:hover .dropdown-content {
    display: block;
}

/* 修改下拉按钮的背景颜色 */
.dropdown:hover .dropbtn {
    background-color: #3e8e41;
}
/* .dropdown:visited.dropdown-content {
    display: inline-block;
}
 */